1. Field of the Invention
This invention relates to means for lifting and lowering long members such as conveyors, booms, and the like. More particularly, the invention relates to means for elevating one end of such elongated members.
2. Information Disclosure Statement
Elongated conveyors are widely used for transporting bulk materials from one location to another. Such conveyors may utilize augers, moving belts, endless chains with buckets or plows, or other mechanisms for moving particular materials. For example, rotating augers are conventionally used to transport grains, forage and silage from ground level to the tops of storage elevators, bins and silos for storage therein. Often, the height of the receiving structure is so high that conveyors exceeding 50 feet (15 meters) in length are required. Auger conveyors up to 150 feet or more (46 meters or more) in length are in use for lifting agricultural materials into storage structures, and are commonly wheel mounted to enable travel between storage and work locations.
Transporting the elongate conveyor from one location to another requires that the auger be lowered to a horizontal or near-horizontal position to clear power lines, avoid tipping of the conveyor, and to conform to the clearance height requirements of public roads. For long conveyors, the angle from the horizontal for such travel necessarily becomes very small.
The mechanism for lifting most elongate augers consists of an articulated undercarriage of two arms extending upward from a base to form a triangle with the elongate auger, the latter generally comprising the hypotenuse. The arms pivot relative to each other at the base. At their outer ends, one arm is pivotally mounted to the elongate member, and the other arm is pivotally mounted to slide or roll on a rail along the elongate member. Thus, the fraction of the elongate member which comprises the upper side of the triangle varies in length during the lifting and lowering operations. In order to raise the conveyor, a winch cable attached to the outer end of the slidably mounted arm is retracted along the elongate member to pull the arm toward an upright position. The required force exerted on the cable to move the arm is a function of the angle between the arm and the elongate member, e.g. the auger. As the angle between the arm and the auger approaches zero, as when the auger is in a recumbent position, the force required to lift the auger is much higher than when the angle is larger. At zero angle, the required lifting force on the cable is theoretically infinite. In other words, a force exerted on the cable by the winch produces no lifting force whatsoever on the arm and elongate auger. Therefore, long augers and other elongate members often must be lifted from a lower position by hydraulic cylinders or other means.